Few things are better than a good unsolved mystery to ignite the imagination. With a tricky puzzle to solve, we can keep ourselves entertained running down leads for ages, no matter if it’s a murder mystery, a strange occurrence in the sky, or a missing boy.

That’s why we’ve put together the 18 craziest, most bizarre unsolved mysteries — from UFOs abducting pilots to a laughing epidemic. These are sure to tickle your imagination!

1. The Valentich Disappearance

A self-proclaimed “flying saucer enthusiast,” 20-year-old Frederick Valentich disappeared on a solo training flight. During the trip, he radioed air traffic control to report another aircraft flying about 1,000 feet above him, adding that his own engine had begun running loudly and roughly. Suddenly, he then uttered, “It’s not an aircraft.” He was never heard from again.